Installing Cementboard New Tub

I am remodeling my old house bathroom and I am installing a new tub and shower base. My wife will be taping the cement board and drywall and wants me to install the board at the ceiling first and work down toward the new tub and shower base. She does not want to stand in the new tub and base and work. Is this a no-no? I had planned to start at the bottom and work up and cut the last piece to fit the ceiling. Opinions and comments appreciated.

Drywall and similar sheet goods are traditionally installed from the top down, and for good reason. There is
neither rule of law nor physics which would preclude doing it the other way. Are you actually putting board
on the ceiling, or just butting up to it? I do not understand your wife's issue: the tub and base certainly must
be installed before the cement board, and much work while standing in a
new tub/shower base is inevitable. Suitable protective measures should be employed. There are usually good
reasons for putting the board joints one place rather than another, and the layout should be worked out before
work commences. Talk to your wife and get it worked out, nicely.

Yes, definitely ceiling should come first. It will help for further wall boarding. I like the idea of Ram Board. It is really wonderful to protect my tub.
Renovate old cabinets with espresso kitchen cabinets and add new look to your kitchen.

If you are installing the cement board on the ceiling you want to do the ceiling first.

If you are installing on the walls I usually start at the bottom and work my way up. Cement board is heavy, and putting the first sheet on overhead and trying to start your screws and hope the sheet doesn't slip at all can be tough. I recommend starting at the bottom and put 1/8" gaps in between each sheet. Read the instructions. I recommend putting 4 mil plastic behind it, but not all cement board manufacturer's require it. I think Durock or Permabase are the easiest brands to install. Selectcrete is the absolute worst.

I recommend protecting the tub and stepping in it (or on it). If you try to do it with a ladder, or something, you'll be at a bad angle and there's a chance the board will slip off and hit the tub. It's easier and safer if you can install it from in the tub.